Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$158.88	4.845%	$166.5777	$166.58	$166.60	$166.60
Purchase #2	$223.77	10.609%	$247.5098	$247.51	$247.50	$247.50
Purchase #3	$10.64	8.206%	$11.5131	$11.51	$11.50	$11.50
Purchase #4	$198.73	6.215%	$211.0811	$211.08	$211.10	$211.10
Purchase #5	$89.82	4.506%	$93.8673	$93.87	$93.85	$93.90
Purchase #6	$164.48	8.510%	$178.4772	$178.48	$178.50	$178.50
Purchase #7	$92.48	3.442%	$95.6632	$95.66	$95.65	$95.70
7 purchase totals =	$938.80		$1,004.6894	$1,004.69	$1,004.70	$1,004.80